When a problem arises immediately after any work was done, that repair would always be my first suspect, and it's guilty until proven innocent. Regardless of the supposedly good leak down test, I'd be concerned that the belt jumped 1 tooth first (the skip), and then jumped further, trashing the valves (the no start). Or it could be as simple as a connector that was not 'clicked' in solid, first loosened, and then completely disconnected.

Yes, the current issue could be caused by a number of other things as well (unrelated to the original work), but I'd want to first make 100% certain it's not something related to what was done previously.

Thanks so much! I will pass this on to my mechanic. Went to the shop this morning and a guy over there that didn't know me found out that I am the owner of the "Green" car. He told me it is a POS in other words, but the car is in great shape. It was running great they told me then as soon as it warmed up, it started skipping again.

The guy I bought the car from told me that the original replacement head he put on had the cam shaft bolts loose and it didn't have any cam seals in it.

I called the shop and updated them with this information, they were going to look into it and get back to me.

Everyone keeps telling me to replace the motor, but from what I have seen of this motor, it is in great shape (cylinders are clean without scoring, pistons are good too).

The #2 cyl just seems to be an issue. The owner told me that maybe whomever owned it before me ran it too long with the #2 cyl skipping and it might have worn out the ring. Your thoughts on this?

Is it throwing any engine codes? A bit more information would be very helpful.

Xintersecty is right, if the rings are bad on #2, then the leak down test would have shown that clear as day. If it passed the leak down, the bottom end of the engine isn't causing the issue. The valves are going to be good because the leak down also verified that. That really leaves the fuel injectors and spark (plugs, wires, ignition coil, possibly crank or cam position sensor) as possible issues. Another thing to double check is the timing belt timing.

I thought it was just Cyl#2 that had low compression, but it is actually Cyl#2 and Cyl#4 that are having low compression.

He told me that everything seems to be timed correctly.

I asked about the possibility of the motor "jumping a tooth", where it was running perfectly then all of a sudden started skipping again, and he told me he didn't think that had happened. But where it is now low compression on 2 and 4, that seems to lend credence to the fact that something might have happened to the valves on those cylinders.

I am wondering if they used the Chevy shop manual to complete the repair or were doing it based on how they have done this for other cars in the past.

This is not a fly by the night shop, this is an ASE certified shop and they actually are the shop of choice for the town I live in. These are the certifications they have on their website:

... I asked about the possibility of the motor "jumping a tooth", where it was running perfectly then all of a sudden started skipping again, and he told me he didn't think that had happened. ....

Doesn't matter how many certifications the guy has, because 'didn't think' is an unacceptable response. In a case like yours, the correct course of action is to disassemble down to the point of being able to check the timing marks again. Once that's been done, there will be no 'think', because it will be apparent (i.e. fact) if the timing has jumped or not. IMO this is something he should have automatically done, and I'd be extremely suspicious of what's going on with this shop.

And throw in on top of that him reporting one 'good' compression test, followed by a 'bad' one citing 'worn ring', and lots of red flags go up for me. I'll tell you flat out that it's a waste of time relating feedback from this forum to him (he could care less about that). Your only 2 choices are continuing to follow the recommendations of this outfit and hope for the best, or take it somewhere else for another opinion. Good luck with it, whichever way you go.

So the first leak down test was fine but now this second one isn't? I'm a bit confused.

Well, it seems you found your problem though, low compression on 2 & 4 will definitely cause your issues. Sounds like timing or valve issues of some sort to me. The rings would have to be really shot to cause issues, and the leak down would have found that anyways.

Quick question, is it possible to put the cam gears back on incorrectly, or are they slotted so as to not allow them to go on upside down? The mechanic told me that they are wondering if the gears were put in incorrectly.

Could someone provide documentation for the process to replace the head on a 2004/2005 Aveo?

I want to read up on it so I can be more educated on how that whole process goes together. I am wondering if they might have not used that process to replace the head and to set the timing.

What type of damage could happen if a "Normal" head replacing and timing process was applied to this car?

As the mechanic said, the car ran perfectly for 10 to 15 minutes then started skipping again.